1. Field of the Invention
The present invention relates to a video surveillance system, and more particularly, to a method for calculating a transform coordinate on a second video of an object having a target coordinate on a first video and related operation process and video surveillance system.
2. Description of the Prior Art
In recent years, due to the explosive development of video processing technology and abrupt reduction of hardware expense, a video surveillance system, such as a camera, is becoming one of the most popular electronic devices.
Concerning whether or not having a Pan/Tilt/Zoom (PTZ) function, cameras can be categorized into two types: fixed and PTZ cameras.
A fixed camera has the capability to keep any suspicious people in an environment where the fixed camera is installed under surveillance. However, despite the surveillance of an intruder existing in the environment, the fixed camera, without the PTZ function, still cannot provide sufficient information about the intruder if a video of the intruder is located in a corner of a fixed video generated by the fixed camera, or the intruder stands far from the fixed camera and the video of the intruder is too small to be identified.
A PTZ camera is designed to overcome the above problems. When detecting that an intruder existing in an environment where the PTZ camera is installed, the PTZ camera moves a video of the intruder to a central region of a PTZ video generated by the PTZ camera with the Pan/Tilt function, and zooms in the video of the intruder with the Zoom function. In result, a user of the PTZ camera can see a face of the intruder clearly and identify the intruder.
However, in the process of moving and zooming-in the video of the intruder, the PTZ camera has no further strength to spare for monitoring another intruder existing in the environment. In short, the PTZ function of the PTZ camera is realized at the expense of a looking-around capability of monitoring all suspicious people in the environment.
Please refer to FIG. 1, which is a schematic diagram of a video surveillance system 10 having both of the looking-around capability of the fixed camera and the PTZ capability of the PTZ camera according to the prior art. The video surveillance system 10 comprises a metal rod 12, a fixed camera 14 fixed on a first end of the metal rod 12, and a PTZ camera 16 fixed on a second end of the metal rod 12. The fixed camera 14 and the PTZ camera 16 are electrically connected together and face toward an identical predetermined direction.
The surveillance process of the video surveillance system 10 on suspicious people in an environment where the video surveillance system 10 is installed is described in brief as follows: When an intruder 22 intrudes in the environment, a video 24 of the intruder 22 will appear in a fixed image plane 18 generated by the fixed camera 14. A target coordinate (x,y) is assumed to be a position where the video 24 is located in the fixed image plane 18, and a transform coordinate (x′,y′) is assumed to be another position where a video 26 of the intruder 22 is located in a PTZ image plane 20 generated by the PTZ camera 16; Then, the PTZ camera 16 moves a video on a correcting coordinate (xD,yD) of the PTZ image plane 20 to a central region of the PTZ image plane 20 with the Pan/Tilt function, and zooms in a video in the central region of the PTZ image plane 20 with the Zoom function. Due to a disparity factor resulting from the fact that the fixed camera 14 is located from the PTZ camera 16 by a finite distance of the length of the metal rod 12, the correcting coordinate (xD,yD) is not exactly equal to the target coordinate (x,y). That is to say, the correcting coordinate (xD,yD) is derived from the target coordinate (x,y) after taking the disparity factor into account.
Since the fixed camera 14 and the PTZ camera 16 are both fixed to the metal rod 12 and face toward the predetermined direction, and the disparity factor is negligible due to too short the length of the metal rod 12, the correcting coordinate (xD,yD) is approximately equal to the transform coordinate (x′,y′), and the PTZ camera 16, in equivalent, shifts and zooms in the video 26 located on the transform coordinate (x′,y′) of the PTZ image plane 20.
Therefore, a user of the video surveillance system 10 can still monitor another intruder existing in the environment at a time when the user is watching the clear Panned/Tilted/Zoomed intruder's 22 face displayed on the PTZ image plane 20.
However, since the PTZ camera 16 is installed according to a coordinate where the video 24 of the intruder 22 is located in the fixed image plane 18, that is not the transform coordinate (x′,y′) but the target coordinate (x,y), to PTZ a video located on the correcting coordinate (xD,yD) of the PTZ image plane 20, the fixed camera 14 cannot be installed far from the PTZ camera 16, and the metal rod 12 cannot be too long, or what the PTZ camera PTZs is not the video 26 or a video neighboring the video 26, but another unexpected video far from the video 26 of the PTZ image plane 20. The user therefore will not see the intruder's 22 face in the PTZ image plane 20 generated by the PTZ camera 16.
Moreover, since the fixed camera 14, and the PTZ camera 16 as well, is fixed to the metal rod 12 to generate a video, and the length of the metal rod 12 has a close relation with the disparity factor of the fixed camera 14 and the PTZ camera 16, the video surveillance system 10 has to be adjusted elaborately before handed over to a user, so that the PTZ camera 16 can PTZ the video 26 as precise as possible. On the other hand, the fixed camera 14 and the PTZ camera 16 of the elaborately adjusted video surveillance system 10 can be applied nowhere but fixed to the metal rod 12. In consequence, the video surveillance system 10 has a fixed disposition of the fixed camera 14 and the PTZ camera 16 on the metal rod 12, and neither the fixed camera 14 nor the PTZ camera 16 can be installed on another position of the metal rod 12 to meet a user's special demand.
In last, since the video surveillance system 10 cannot function well without the elaborately adjusting process, and the fixed camera 14 of the well-adjusted video surveillance system 10 cannot operate together with another PTZ camera but the PTZ camera 16 only, the video surveillance system 10 including the fixed camera 14 and the PTZ camera 16 cannot be sold in pieces, but in a whole set.